Apparatus for working flat, flexible material

ABSTRACT

This invention relates to apparatus for working flat, flexible material by means of working members opposing each other. One of the working members is driven back and forth toward and away from the other working member. A piston to which the other working member is connected, is subject to a pressure from a pump and subject to a reset force whereby the piston may be adjusted to predetermined starting elevational positions to provide a desired working pressure. A pressure relief valve assures that the piston yields when the working pressure exceeds said desired pressure and returns to said starting position when the working pressure is reduced again. In a further embodiment an auxiliary pressure space of selectively variable volume is provided for adjusting said piston to different elevational starting positions even during the operation of the apparatus.

United States Patent Dokoupil [4 1 July 18, 1972 54] APPARATUS FORWORKING FLAT, 3,298,267 1/1967 Schmid et al. ..100/257 x FLEXIBLEMATERIAL FOREIGN PATENTS OR APPLICATIONS 2 I t D k l l [7 1 Obemrse Ger813,060 5/1969 Canada ..69/33 [73] Assignee: Maschineniabrik Turner AG,Oberursel, Primary ExaminerAlfred R. Guest Germany Attorney-W. G. Fasse[22] Filed: Aug. 19, 1970 ABSTRACT [2]] Appl' 65280 This inventionrelates to apparatus for working flat, flexible material by means ofworking members opposing each other. [30] Foreign Application PriorityData One of the working members is driven back and forth toward and awayfrom the other working member. A piston to which fii i 3 g3 the otherworking member is connected, is subject to a presy y sure from a pumpand subject to a reset force whereby the [52] U S Cl 69/33 loo/257267/130 piston may be adjusted to predetermined starting elevational [511 U40 positions to provide a desired working pressure. A pressure re- I58] Field 1 00/257. lief valve assures that the piston yields when theworking pres- 267/136 sure exceeds said desired pressure and returns tosaid starting position when the working pressure is reduced again. In afurther embodiment an auxiliary pressure space of selectively [56]References Cited variable volume is provided for adjusting said pistonto dif- UNITED STATES PATENTS ferent elevational starting positions evenduring the operation of the a aratus. 1,671,365 5/1928 Hatch ..267/l30pp 3,005,404 10/ l 961 Tucker 100/257 14 Claims, 2 Drawing FiguresPATENTED JUL 1 8 I972 SHEET 1 [IF 2 FUWUUW? INVENTOR J DOKOUPIL PATENTED1mm: 3,677,041 SHEET 2 or 2 INVENTOR 31m .DOKOUP/L APPARATUS FOR WORKINGFLAT, FLEXIBLE MATERIAL The present invention relates to apparatus forworking flat, flexible material, for example leather, especially forsoftening leather. Such working or softening is accomplished by twoworking members arranged opposite each other to form a gap through whichthe material is fed. The spacing between the working members isperiodically increased and decreased by moving the working membersrelative to each other whereby pressure is exerted sequentially on thematerial being worked to achieve the desired result such as softening.

If leather is to be worked the working members are provided withprotrusions or corrugations facing each other in such a manner that theprotrusions on one working member reach into the valleys between theprotrusions on the other working member when the working membersapproach each other periodically. Thus the leather is stretched andsoftened.

OBJECTS It is an object of the invention to provide in accordance withthe material to be worked, a respective working pressure, morespecifically, a working pressure which is adapted to the kind ofmaterial, especially leather which is being treated.

Yet another object is to adjust one of said working members of theapparatus to such a starting elevational position that due to suchstarting position and the relative movement between the working members,a certain minimum spacing between the working members could not beexceeded, that is, the working members must not get closer together thansaid minimum spacing so that the working pressure will not reach valueslarger than those determined by said minimum spacing.

A further object of the invention, especially in connection with leatherworking, is to assure that the extent to which the protrusions on oneworking member enter into the valleys of the other working member isadjustable to obtain a corresponding stretching without overstretching.Stated differently, it is desired to control the stretching, forexample, to make it the smaller the less the protrusions enter into thevalleys and vice versa.

Another object of the invention is to make said adjustment of theinteraction of the working members especially simple for the operator.

A still further object is to assure that one of the working members willmaintain its selectively adjusted position until a predetermined workingpressure is reached and will yield as soon as such pressure is reachedor exceeded, and that said member will return to said position as soonas the working pressure decreases again below the predetermined valuewhereby a maximum working pressure will not be exceeded.

Yet another object of the invention is to provide an apparatus of thementioned type wherein a quantity of working fluid, for example ahydraulic working fluid, which has been displaced by the yielding of oneworking member will not be replenished so that the one working memberwill automatically assume, after a rough adjustment by an operator, anoperational elevational position such that a maximum working pressurecannot be exceeded.

A still further object of the invention is to assure that the adjustmentof the working position of said one working member can be adapted tochanges in the working conditions as they may occur, for example due tothe fact that the leather may vary in thickness and/or stiffness. Forthis purpose the working fluid displaced by a yielding of one workingmember is to be replenished automatically as soon as the workingpressure is again decreased below a predetermined maximum value.

Another object is to provide means which permit the continuouspositional adjustment of one working member in response to varying orchanging working conditions even while the apparatus is in operation.

SUMMARY OF THE INVENTION According to the invention there is provided anapparatus for working flat, flexible material, especially for softeningleather wherein one working member is adjustable by pressure means, forexample hydraulic pressure means, to elevational starting positionagainst a reset force, whereby the hydraulic pressure means limit theworking pressure occurring during the operation of the apparatus bypermitting a yielding of one of the working members when the operationalpressure exceeds a maximum working pressure, and which pressure meansprevent said yielding as soon as the working pressure has decreased tosaid maximum pressure or below said maximum pressure.

The moving of one of the working members to its starting elevationalposition is best, but not exclusively accomplished by hydraulic pressuremeans known as such, whereby such movement is against said reset forcefurnished, for example, by a compression spring. It is an advantage ofthe invention that it is not necessary to ascertain whether or not acertain elevational position has yet been reached by one of the workingmembers, because the working pressure will be automatically limited bythe yielding of one of the working members when the working pressurereaches a predetermined maximum value whereby the desired workingpressure cannot exceed said predetermined value. Stated differently, themaximum working pressure does not result from the starting elevationalposition of one of the working members but rather it is determined bythe pressure value to which said hydraulic pressure means have beenadjusted. As a result the operation of the apparatus has beensubstantially simplified.

Another important advantage of the invention is seen in that thematerial being treated cannot be overworked. This is rather essential,especially in connection with leather which may rip when it isoverstretched. The invention avoids such drawbacks.

In one embodiment the hydraulic pressure means are constructed andarranged so that the hydraulic liquid which has been displaced duringthe yielding of said one working member, will not be replaced during thecontinuing operation. As a result the one working member adjusts itselfautomatically to an elevational position which will then assure thatduring the continuing periodic and relative movement of the workingmembers the maximum working pressure will not be exceeded. This meansthat the initial adjustment by the operator of one of the workingmembers to a starting elevational position is in effect a roughadjustment, whereupon the one working member in the apparatus accordingto the invention assumes automatically the desired operationalelevational position.

In another embodiment of the invention it is possible to continuouslyadapt the elevational position of one of the working members to thevarying operational conditions, for example the thickness of the leathermay vary and so may its stiffness. In this embodiment the pressuremeans, for example, in the form of hydraulic pressure means, are adaptedfor replenishing the quantity of hydraulic working liquid which has beendisplaced by the yielding of said one working member. Such replenishingtakes place during the continuing operation during each increasing ofthe spacing between the two working members and thus during theperiodically decreasing of the working pressure. The one working memberthus returns in this embodiment repeatedly into its initially adjustedstarting elevational position from which it yields sufficiently so thatthe desired maximum working pressure will not be exceeded. Hence, acontinuous adjustment or adaptation of the apparatus to the varyingoperational conditions resulting, for example, from varying propertiesof the material being treated, has been provided.

In still another embodiment of the invention it is possible to adjustthe starting elevational position of the one working member even duringthe operation of the apparatus. This has been accomplished by connectinga pressure fluid filled space to said hydraulic pressure means, wherebythe volume of said space is selectively variable, for example, by meansof a control valve.

rnrm: nun

In order that the invention may be clearly understood, it will now bedescribed by way of example, with reference to the accompanyingdrawings, wherein:

FIG. 1 illustrates an apparatus for the softening of sheet material,such as leather, and

FIG. 2 illustrates a partial view of the apparatus according to FIG. 1and including additional means for varying the starting elevationalposition of the working elements.

The apparatus shown in FIG. 1 is especially useful for softening ofleather. FIG. 1 illustrates only those elements which are essential forthe understanding of the invention. Any other structural members,especially the drive for causing a periodical relative motion of theworking members may comprise well known means.

The present apparatus comprises an upper working member or element 3which is not actively driven, and a lower working member or element 4supported on drive means D. Such drive means impart to the workingmember 4 a back and forth movement as indicated by the double arrowshown below the working member 4. Both working members 3 and 4 areprovided with protrusions or corrugations 7 and 8 which are displacedrelative to each other and laterally in such a manner that theprotrusions 7 fit into the valleys between the protrusions 8 and viceversa when the two working members 3 and 4 are advanced toward eachother. This arrangement of the protrusions which permits their grippinginto each other so to speak assures that the sheet material, especiallyleather, which is fed through between the working members will besimultaneously bent as well as stretched. Such bending and stretching ofthe leather is well known in the art.

The working member 3 is suspended from a piston 1 which is glideablysupported in the cylinder 9. The cylinder 9 is supported by a carrier orbeam 10 of the machine frame, the details of which are not shown.Sealing rings 11 and 12 assure a proper sealing between the piston 1 andthe wall of the cylinder 9. The top of the cylinder 9 is closed by aring flange or plate 13 and the piston 1 is shown in its upper restposition in which the upper end of the piston 1 bears against saidflange or plate 13 which is attached to the upper end of the cylinder 9by means of bolts 14 and 15. A sealing gasket is suitably positionedbetween the top of the cylinder 9 and the flange 13. The flange 13 andthus the cylinder 9 is closed by means of a bell shaped cover 16 whichis fastened to the cylinder 9 also by said bolts 14 and 15. A furthersealing gasket is located between the flange I3 and the cover 16 wherebythe top of the apparatus is properly sealed.

The piston l is maintained in its shown rest position by means of acompression spring 2 which presses the piston 1 upwardly against theflange 13. The compression spring 2 is located in a bore 17 of thepiston 1. A shaft 18 having a flange 19 at its lower end is surroundedby the compression spring 2 and reaches into said bore 17. Thecompression spring 2 bears against the flange 19. The upper end of theshaft 18 extends into a threaded shank 20 which extends through anaperture in the flange or plate 13. A nut 21 holds the shaft 18 in itsdesired position.

The compression spring 2 which bears with its lower end against theflange 19 at the lower end of the shaft 18 presses with its upper endagainst an insert member 22 which is secured in the bore 17 of thepiston 1 at the upper end thereof,

for example, by means of a threaded connection. The insert member 22closes the bore 17 except for the apertures 27 the purposes of whichwill be described below. The shaft 18 is held in a fixed position by thenut 21 which rests on the flange 13. Furthermore, the compression spring2 presses the insert member 22 and thus the piston 1 upwardly becausethe flange 19 is rigidly secured to the lower end of the shaft 18.Therefore, the piston 1 bears in its rest position against the flange13. In this connection it should be noted that the aperture through theinsert member 22 through which the shaft 18 extends is large enough tofreely permit a back and forth motion of the piston 1 relative to theshaft 18.

The cover member 16 has a hole in the top of its bell shape to which isconnected a Tee-pipe fitting 23. The left hand port of the Tee-pipefitting 23 is connected to a pressure supply source such as pump 24. Theright hand port of the Tee-pipe fitting 23 is connected to a maximumpressure valve 5.

Hydraulic fluid, for example, liquid such as oil under pressure suppliedby the pump 24 is fed into the inner space 25 of the cover 16. The fluidpasses through the apertures 26 in the flange 13 and through apertures27 in the insert member 22 whereby it enters into the bore 17 of thepiston 1. Thus, a pressure is built up in the bore 17 of the piston 1.Such pressure is effective against the force of the compression spring2. When the pressure exceeds the force of the compression spring 2 thepiston l is caused to move downwardly whereby the working member 3 ismoved in the direction toward the working member 4 arranged opposite theworking member 3. The duration or length of this motion is determined bythe amount of fluid or liquid supplied or by its pressure because agiven pressure will be reached in the bore 17 in response to a givensupply pressure with reference to the increasing force or tension of thecompression spring 2 which is compressed as the piston 1 movesdownwardly. The given supply pressure of the hydraulic liquid suppliedby the pump or the amount of the supplied liquid are easily adjustableby well known means. In this manner it is therefore possible to adjustthe working member 3 in a predetermined position which will be referredto as its starting position.

The apparatus illustrated in FIG. 1 operates as follows. When during theperiodical back and forth movement of the driven working member 4 apressure is exerted upon the working element 3 for example, due to thefact that the leather is exceptionally stifi', so that the exertedpressure exceeds the pressure resulting from the adjusted position ofthe working member 3, the maximum pressure valve 5 will respond wherebypressure medium may escape through the return conduit into a sump orcollecting container not shown. As a result, the piston 1 may yield toan extent corresponding to the volume of the escaping pressure medium.With the yielding of the piston 1 the working member 3 attached topiston 1 also yields backwardly until the pressure which exceeded thepres sure to which the maximum pressure valve 5 has responded, isreduced to a value just below such response value. In this instant, themaximum pressure valve 5 will close again whereby the piston l and thusthe working member 3 are stopped so that it will now take up anoperational elevational position which is now adapted to therequirements of the material being treaded, for example, to the factthat the leather is exceptionally stifi so that it could not be handledwith the working member 3 in its starting elevational position. In orderto prevent during the further operation the replenishing of the pressuremedium which has been displaced due to the yielding movement of theworking member 3, a manually operated closure valve 28 is provided inthe conduit to the pump 24. The closure valve 28 prevents subsequent toreaching the operational elevational position the supply of any pressuremedium from the pump into the bore 17. Accordingly, the working member 3remains in its operational elevational position during the furthertreatment of the sheet material so that overstraining or undue wear andtear of the material being treated is prevented. This is an importantadvantage of the invention, especially, since it also prevents anydamages to the apparatus itself.

'Another advantage of the present invention is seen in that theoperational elevational position of the working member 3 is continuouslyadjustable in response to the variable instantaneous operationalconditions which, for example, may vary due to differing thicknesses ofthe leather being treated. For this purpose, the closure valve 28 iseither not used or it is maintained in its open position so that theamount of pressure medium which has been displaced by the yieldingmovement of the piston 1, will be replenished in response to theperiodically and repeatedly decreasing working pressure. This periodicaldecrease of the working pressure results due to the back and forthmovement of the driven working member 4. As a result, the piston 1 willrepeatedly return to its originally adjusted starting elevationalposition in response to the decrease of the working pressure. Suchstarting elevational position, for example, may be defined by a certainpressure delivered by the pump 24. As described, it is possible toadjust the starting elevational position of the piston 1 anywhereintermediate its upper and lower end positions. However, it is evensimpler to move the piston 1 to a fixed starting elevational position bysupplying sufficient pressure or volume of a pressure medium so that thepiston 1 will bear against a stop ring 30 with its shoulder 29. As soonas the pump 24 has moved the piston 1 with its shoulder 29 against thestop ring 30 the operation of the apparatus may be started whereby theabove described process steps will take place in response to theoccurrance of pressures exceeding a maximum pressure as determined bythe maximum pressure response valve 5. However, in response to thereduction of the working pressure due to the return stroke of theworking member 4 the pump will repeatedly replenish the amount ofpressure medium which has been displaced through maximum pressure valve5. Thus, the piston 1 will always be returned to bear with its shoulderagainst the stop ring 30.

It should be noted that the maximum pressure valve 5 is adjustable sothat any desired response pressure and thus the maximum working pressuremay be established. Such adjustable maximum pressure valves are wellknown in the art.

The apparatus illustrated in FIG. 1 may be modified so that the startingelevational position of the piston 1 may be varied even during theoperation of the apparatus. This may be accomplished by rather simplemeans in that a volume variable space is connected to the pressuremeans, for example the hydraulic pressure means whereby the variablevolume space is filled with a pressure medium.

The space which is connected with the hydraulic pressure means takes upa predetermined amount or quantity of pressure fluid in response to itsadjusted position or rather in response to its instantaneous adjustedposition. The pressure medium yields in response to the increasing ordecreasing volume of said space whereby one of the working members 3 or4 are moved correspondingly. Thus, when the volume is being enlarged oneof the working elements is displaced away from the other working elementwhereas upon decreasing the volume of the space one working element ismoved toward the other working element. Therefore, a decrease of theworking intensity will result from the movement of the working membersaway from each other. On the other hand, an increase of the workingintensity will result from the movement of the working members towardeach other.

An embodiment for performing the just described function is illustratedin FIG. 2 which also partially illustrates the apparatus of FIG. 1. Onlythose structural features are shown which are essential for theunderstanding of the apparatus according to FIG. 2. Especially, theworking member 4 has been omitted from FIG. 2. Only the working member 3which is adjustable in its starting elevational position, is shown inFIG. 2. The functional details of the adjustable working member 3 aredescribed in connection with FIG. 1 and reference to FIG. 1 should behad in this connection. The same structural elements are designated bythe same reference numerals in both Figures. Moreover, the workingmember 3 is supported in the cylinder 9 and adjustable to its startingelevational position as described in detail with reference to FIG. 1.

As in FIG. 1, the adjustment of the working member 3 to its startingelevational position is accomplished by supplying pressure medium fromthe pump 24 into the space 25 and thus also into the bore 17. The pumpfurther supplies pressure medium to the maximum pressure responsivevalve 5. As a result of the pressure built-up in the space 25 as well asin the bore 17 the upper working member 3 is displaced downwardly into aposition defining the starting elevational position. Thus, the pump 24and the maximum pressure valve 5 represent the above mentioned hydraulicpressure means.

A space 39 in a housing or auxiliary cylinder 31 is connected with aninlet port 38 through a conduit 40 to said hydraulic pressure means. Thespace 39 contains an auxiliary piston 32 which is freely movable withinthe auxiliary cylinder or housing 31 and thus in the space 39. The upperlimit of motion for the piston 32 is determined by the housing wall 35whereas the lower limit of motion of the piston 32 is determined by thestop member 45. Within these limits the piston motion is variable tothus vary the volume of the space 39. The stop member 45 is formed by anend face at the upper end of a threaded spindle 36 the function of whichwill be described below. The selected height of the variable space 39 isrepresented by the reference numeral X. The lower end of the spindle 36protruding from the cylinder 31 is provided with a scale or dial 37 thusgiving an indication of the presently adjusted position of the stopmember 45 which is directly indicated by the extent to which the lowerend of the spindle 36 protrudes from the cylinder 31. The adjustment ofthe instantaneous position of the stop member 45 is accomplished bysimply turning the threaded spindle 36.

Let it be assumed that the upper working member 3 is in its startingelevational position whereby the piston 32 has taken up the position inwhich it is shown in FIG. 2. In this position the piston 32 is pressedagainst the stop member 45 by the pressure prevailing in the hollowspace or volume 39 which pressure corresponds to that in the space 25due to the direct connection through conduit 40.

The just described arrangement operates as follows. If in the course ofa working or treatment of a sheet material the working intensity is tobe increased, it is necessary for this purpose to adjust the startingelevational position of the upper working member 3 in the directiontoward the other working member 4 which is not shown in FIG. 2.Accordingly, the working member 3 will be displaced downwardly and thepiston 32 will have to be displaced upwardly that is in the directiontoward the cylinder closing or housing wall 35. In order to displace thepiston 32 in the desired just described manner a pressure P1 is suppliedto the pressure volume 43 in the cylinder 31. This pressure P1 is largerthan the pressure P2 in the pressure space 39. Both pressures aresupplied by the pump 24. The pressure space 43 has an inlet port 42through which it is connected by means of a conduit 47 and through adistributing valve 41 continuing through the conduit 47 and through adistributing 46 to the pump 24. When the distributing valve 41 isswitched from its shown position I in which the conduit 47 is connectedto a return conduit R, to the position ll, fluid under pressure will besupplied from the pump to the volume 43 whereby the piston 32 isdisplaced upwardly and whereby fluid under pressure is displaced out ofthe volume 39 through the connecting conduit 40 into the inner space 25and thus into the bore 17 of the piston 1. As a result of the enteringof fluid under pressure into the space 25, the piston 1 to which theworking member 3 is connected must yield downwardly whereby the justmentioned desired increased working intensity is achieved. A maximumpressure responsive valve 44 limits the pressure supplied by the pump 24to such a value that the pump will not be able to damage itself bydeveloping too large a pressure.

If it is now desired to reverse the just mentioned downward displacementof the working member 3, that is, if the originally adjusted startingelevational position is to be resumed, the distribution valve 41 is tobe returned to its shown position I whereby the pressure fluid isremoved from the space 43 through the conduit 47 and through the returnconduit R. The removal of the pressure medium from the space 43, isaccomplished as a result of the pressure which is effective in thevolume or space 39 which pressure is the same as that in the space 25and in the bore 17. As described above with reference to FIG. 1, thecompression spring 2 drives the piston 1 back up whereby the pressuremedium flows out of the bore 17 and out of the space 25 through theconnecting conduit 40 into the space 39.

In this manner the piston 32 is enabled to slide back until it comes torest against the stop member 45. When the piston 32 has reached its justmentioned end position, the displacement of pressure medium from space25 and bore 17 is such that the piston l and hence upper working member3 may return into its originally adjusted starting elevational position.It will be seen from the foregoing, that the piston 32 which moves backand forth in the auxiliary cylinder 31, and which is sealed by means ofgaskets 33, 34, thus adjusts selectively an additional working intensitywhich adjustment may take place during the operation of the apparatusbecause the distribution valve may be operated at any time.

If now during the treating or working of the sheet material an increaseor a decrease of the working pressure is desired, the startingelevational position of the working member 3 is adjusted by positioningthe piston 32 approximately intermediate the stop member 45 and the wall35 of the auxiliary cylinder 31. Thus it is possible to increase theworking pressure by displacing the piston 32 from its center positiontoward the wall 35, or to decrease the working pressure by displacingthe piston 32 toward the stop member 45. For this purpose thedistribution valve 41 is adjusted either to its position [I or to itsposition i.

If an especially large range of pressure variations is desired, thethreaded spindle 36 will have to be turned so that its end extendscorrespondingly far out of the housing of the auxiliary cylinder 31whereby a correspondingly large length x will result.

Although specific examples have been described, it is to be understoodthat the invention is intended to cover all modifications andequivalents within the scope of the appended claims.

What I claim is:

1. In an apparatus for working flat, flexible material by means of afirst working member and a second working member, each working memberhaving a respective working surface arranged to face the working surfaceof the other working member to provide a spacing between said workingsurface for feeding said flat, flexible material through said spacing,drive means operatively connected to said first working member formoving the first working member toward and away from the second workingmember whereby said spacing between the first and second working membersis periodically decreased and increased and a working pressure isexerted on said material, wherein pressure means are operativelyassociated with one of said working members for adjusting said oneworking member to a starting position, said pressure means limiting theworking pressure to a predetermined value by permitting a yielding ofsaid one working member when the working pressure exceeds saidpredetermined value and until the working pressure is decreased againbelow said predetermined value, the improvement comprising a piston andcylinder means for confining a single pressure chamber in which saidpiston is movable, means for securing said cylinder means in astationary position, said second working member being connected to saidpiston, means for connecting said pressure means to said single pressurechamber whereby said piston and with it said second working member areadjustable to said starting position and to perform said yielding, andreset means as well as means for locating said reset means in thecylinder means for exerting a reset force on said piston.

2. The apparatus according to claim 1, wherein said pressure means arehydraulic pressure means including a pump and a pressure responsivemember, piping means for connecting said pump and said pressureresponsive member to said single pressure chamber, and a fluid controlvalve in said connecting piping means for preventing during furtheroperation of the apparatus the replenishing of a quantity of hydraulicworking fluid which has been displaced through said pressure responsivemember by the yielding of said piston and second working member.

3. The apparatus according to claim 2, wherein said pressure responsivemember is adjustable for responding to different ressures.

. e apparatus according to claim 1, wherein sard pressure means arehydraulic pressure means including a pressure responsive member and apump for continuously replenishing a quantity of hydraulic working fluidin response to the dis placement of such fluid by the yielding of saidpiston and second working member, whereby said replenishing takes placeduring the increasing of said spacing between the first and secondworking members and thus during the periodically decreasing workingpressure.

5. The apparatus according to claim 4, wherein said piston and cylindermeans include cooperating stop means for defining outer limits ofmovement for said piston.

6. The apparatus according to claim 1, wherein said reset force exertingmeans is a compression spring.

7. The apparatus according to claim 6, wherein said piston has alongitudinal bore with an open end and a closed end, said compressionspring locating means comprising a shaft having a threaded end and aflanged end, said shaft extending longitudinally through the compressionspring so that one end of the spring rests on said flanged end of theshaft, an apertured closure member for closing said open end of thepiston, said shaft extending through a central aperture of said closuremember whereby the other end of said spring bears against said closuremember inside said piston bore and whereby the threaded end of the shaftprotrudes from said central aperture, and means for securing thethreaded shaft end to said cylinder.

8. The apparatus according to claim 1, further comprising means fordefining a selectively variable volume, means for connecting saidvariable volume to said pressure means, whereby the variable volume maybe filled with a pressure medium.

9. The apparatus according to claim 8, wherein said pressure meansinclude a single pump connected to said variable volume and to saidcylinder.

10. The apparatus according to claim 8, wherein said means for defininga selectively variable volume comprise an auxiliary piston cylindermeans, conduit means for connecting said auxiliary cylinder means tosaid pressure means, and means for selectively adjusting the position ofsaid auxiliary piston means in said auxiliary cylinder means to definesaid variable volume between a surface of said auxiliary piston and saidauxiliary cylinder means.

11. The apparatus according to claim 10, wherein said means forselectively adjusting the position of the auxiliary piston meanscomprises a threaded bore in said auxiliary cylinder means, a threadedshaft extending through said bore into the auxiliary cylinder meanS sothat an end face of said shaft inside the cylinder means provides a stopfor the auxiliary piston means, said threaded shaft having an endportion without threads extending out of said auxiliary cylinder means,and dial means on said end portion for indicating the extent to whichthe end face reaches into said auxiliary cylinder means.

12. The apparatus according to claim 10, wherein said auxiliary cylindermeans is divided into two spaces above and below said auxiliary pistonmeans, said means for connecting including a first conduit forconnecting one of said spaces to said pressure means, said apparatusincluding further pressure means, a second conduit for connecting theother space to said further pressure means, a return conduit, andcontrol valve means in said second conduit for selectively connectingthe other space to said further pressure means and to said returnconduit.

13. The apparatus according to claim 12, wherein said pressure means andsaid further pressure means are comprised in a single pump.

14. The apparatus according to claim 12, further comprising selectivelyadjustable pressure relief means connected to said second conduit.

i l k UNKTED STATES PATENT @FFMJE (JERMWCATFE @F MERPLEQTWN Patent No. 35YY Q H. Dated July 18, 1972 Inventor s) Jirf. Dokoupil It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

On the cover sheet [36] the filing date "Augv 8, 1969 of German PatentApplication P 19 '42 41609, should read Ange 20, 1969 Signed and sealedthis 19th day of December 1972.

(SEAL) Atteet:

EDWARD MOFLETGKERJRO ROBERT GOMSGFK Attesting Officer" Commissiener ofPatents FORM PC4050 (10-69) 1 USCOMM-DC 60376-P69 a U.$. GOVERNMENTPRINTINIG OFFICE: 569 0'365-334,

1. In an apparatus for working flat, flexible material by means of afirst working member and a second working member, each working memberhaving a respective working surface arranged to face the working surfaceof the other working member to provide a spacing between said workingsurface for feeding said flat, flexible material through said spacing,drive means operatively connected to said first working member formoving the first working member toward and away from the second workingmember whereby said spacing between the first and second working membersis periodically decreased and increased and a working pressure isexerted on said material, wherein pressure means are operativelyassociated with one of said working members for adjusting said oneworking member to a starting position, said pressure means limiting theworking pressure to a predetermined value by permitting a yielding ofsaid one working member when the working pressure exceeds saidpredetermined value and until the working pressure is decreased againbelow said predetermined value, the improvement comprising a piston andcylinder means for confining a single pressure chamber in which saidpiston is movable, means for securing said cylinder means in astationary position, said second working member being connected to saidpiston, means for connecting said pressure means to said single pressurechamber whereby said piston and with it said second working member areadjustable to said starting position and to perform said yielding, andreset means as well as means for locating said reset means in thecylinder means for exerting a reset force on said piston.
 2. Theapparatus according to claim 1, wherein said pressure means arehydraulic pressure means including a pump and a pressure responsivemember, piping means for connecting said pump and said pressureresponsive member to said single pressure chamber, and a fluid controlvalve in said connecting piping means for preventing during furtheroperation of the apparatus the replenishing of a quantity of hydraulicworking fluid which has been displaced through said pressure responsivemember by the yielding of said piston and second working member.
 3. Theapparatus according to claim 2, wherein said pressure responsive memberis adjustable for responding to different pressures.
 4. The apparatusaccording to claim 1, wherein said pressure means are hydraulic pressuremeans including a pressure responsive member and a pump for continuouslyreplenishing a quantity of hydraulic working fluid in response to thedisplacement of such fluid by the yielding of said piston and secondworking member, whereby said replenishing takes place during theincreasing of said spacing between the first and second working membersand thus during the periodically decreasing working pressure.
 5. Theapparatus according to claim 4, wherein said piston and cylinder meansinclude cooperating stop means for defining outer limits of movement forsaid piston.
 6. The apparatus according to claim 1, wherein said resetforce exerting means is a compression spring.
 7. The apparatus accordingto claim 6, wherein said piston has a longitudinal bore with an open endand a closed end, said compression spring locating means comprising ashaft having a threaded end and a flanged end, said shaft extendinglongitudinally through the compression spring so that one end of thespring rests on said flanged end of the shaft, an apertured closuremember for closing said open end of the piston, said shaft extendingthrough a central aperture of said closure member whereby the other endof said spring bears against said closure member inside said piston boreand whereby the threaded end of the shaft protRudes from said centralaperture, and means for securing the threaded shaft end to saidcylinder.
 8. The apparatus according to claim 1, further comprisingmeans for defining a selectively variable volume, means for connectingsaid variable volume to said pressure means, whereby the variable volumemay be filled with a pressure medium.
 9. The apparatus according toclaim 8, wherein said pressure means include a single pump connected tosaid variable volume and to said cylinder.
 10. The apparatus accordingto claim 8, wherein said means for defining a selectively variablevolume comprise an auxiliary piston cylinder means, conduit means forconnecting said auxiliary cylinder means to said pressure means, andmeans for selectively adjusting the position of said auxiliary pistonmeans in said auxiliary cylinder means to define said variable volumebetween a surface of said auxiliary piston and said auxiliary cylindermeans.
 11. The apparatus according to claim 10, wherein said means forselectively adjusting the position of the auxiliary piston meanscomprises a threaded bore in said auxiliary cylinder means, a threadedshaft extending through said bore into the auxiliary cylinder meanS sothat an end face of said shaft inside the cylinder means provides a stopfor the auxiliary piston means, said threaded shaft having an endportion without threads extending out of said auxiliary cylinder means,and dial means on said end portion for indicating the extent to whichthe end face reaches into said auxiliary cylinder means.
 12. Theapparatus according to claim 10, wherein said auxiliary cylinder meansis divided into two spaces above and below said auxiliary piston means,said means for connecting including a first conduit for connecting oneof said spaces to said pressure means, said apparatus including furtherpressure means, a second conduit for connecting the other space to saidfurther pressure means, a return conduit, and control valve means insaid second conduit for selectively connecting the other space to saidfurther pressure means and to said return conduit.
 13. The apparatusaccording to claim 12, wherein said pressure means and said furtherpressure means are comprised in a single pump.
 14. The apparatusaccording to claim 12, further comprising selectively adjustablepressure relief means connected to said second conduit.